With Ivory in Short Supply, Pianists Tickle the Polymers

By MALCOLM W. BROWNE

Published: May 25, 1993

IMPORTING ivory into the United States has been illegal since 1989, but a team of engineers, materials scientists and piano builders believes it has developed a piano key to gladden the hearts of musicians as well as elephants.

The existing supply of ivory, traditionally used as a thin veneer to cover wooden piano keys, is being depleted, and conservationists and elephant lovers hope it will grow scarcer still. But many pianists still swear by ivory, and swear at imitations.

Experts at the Rensselaer Polytechnic Institute in Troy, N.Y., have devised a synthetic ivory with a feel and a microscopic structure closely resembling those of natural ivory, and satisfied concert pianists are already playing on keys made of the substance. In an informal blind test of concert grand pianos being conducted by Steinway & Sons, a leading builder of concert pianos, some soloists have chosen those with the new keys for concert performances in preference to those with ivory or conventional plastic.

A shift toward the new material by piano makers is unlikely to have a significant effect on the ivory market and the slaughter of elephants because these manufacturers have never been major consumers of ivory. "Two elephant tusks would provide enough ivory for an entire year of our production -- close to 1,000 pianos," said Daniel Koenig, Steinway's vice president for manufacturing.

Nevertheless, conservationists welcome synthetic ivory, because it could lead to the replacement of natural ivory in many other applications. As stocks of elephant ivory owned by manufacturers around the world are used up, substitutes must be found.

The global treaty of 1990 banning traffic in elephant ivory has been very effective, according to Ginette Hemley of Traffic USA, the trade-monitoring arm of the World Wildlife Fund. Even Japan, traditionally the world's largest consumer of ivory, is strictly observing the ban, she said. Manufacturers of chops, Asian signature stamps, remain the largest consumers of ivory, but even they are turning to other materials.

Although synthetic polymers have been used as the veneer surfaces of many piano keys since the mid-1950's, some concert pianists dislike plastic, complaining that it is too slippery to the touch and that it feels uncomfortably cool.

A $232,000 project headed by Dr. Henry A. Scarton, an associate professor of mechanical engineering at Rensselaer Polytechnic, has created a patented polymer, called RPIvory, that the inventors say resolves these problems.

"We realized at the beginning that a piano key must be smooth but not slippery," Dr. Scarton said, "and that the problem had to be attacked from the viewpoint of the tribologist, an engineer expert in friction."

Another engineer at Rensselaer, Salvadore J. Calabrese, is a tribologist who has made a special study of microscopic surface patterns on materials that slide against each other. Using a scanning electron microscope, he found that the surface of natural ivory, however smooth it may look, is actually covered with randomly oriented microscopic valleys and ridges. Ivory is also filled with numerous microscopic pores, Mr. Calabrese learned.

"Ivory is not slippery," he said, "because it exhibits a stick-slip form of friction; that is, an object moving over an ivory surface alternately slips along for an instant, then sticks for an instant, then slips again. Normally, tribologists try to eliminate this chattering stick-slip motion in bearings and other sliding surfaces. But in this case, our goal was the reverse: we needed to impart stick-slip friction in a polymer surface that normally slides smoothly."

Igor Kipnis, a concert artist who performs on the harpsichord and fortepiano, agrees that many keyboard players object to the slipperiness of conventional plastics. Similarity to Ice-Skating

"It's like ice skating," he said. "Plastic feels different. Unless you're a very cool performer you tend to sweat, and with plastic your fingers have nothing to grip. A lot of harpsichord players use bone keys, or even tortoise-shell keys, which have a better feel than plastic."

Mr. Calabrese said: "We believe that sweaty or oily fingers tend to hydroplane on a piano key made of conventional plastic, like an automobile tire hydroplaning on wet pavement. Because the pores of natural ivory absorb the thin layers of sweat and oil that accumulate on fingers, we believe they give a piano key a surer touch."

But the pores in ivory, which are far too small to see with the naked eye, proved difficult to reproduce in plastic. A solution was found by mixing a liquid polyester with white titanium pigment and very finely powdered polyethylene glycol. After this material hardens, the polyethylene glycol is soaked away with warm water, leaving empty pores approximating those of natural ivory.

"We also had to reproduce the random ridges and valleys as well as the natural grain of ivory," Mr. Calabrese said. "And this we did by making a finely detailed cast of the surface of a real ivory piano key and imprinting it on our polymer keys." Results Called Promising